1. Field of the Invention
The present invention relates to the production of alumina and, more particularly, to the production of alumina which is highly water dispersible.
2. Description of the Prior Art
Alumina, as is well known, has widespread commercial usage in such applications as abrasives, frictionizing paper surfaces, fiberglass surfaces and metal surfaces, as static and soil protection agents on wool, nylon and acrylic carpets, and as dispersing agents in rug shampoos, etc. In such commercial usages, the alumina is typically utilized as a dispersion or suspension, the alumina being present in an aqueous acid solution having a pH generally in the range of from about 2 to about 4, the acid serving to act as a peptizing agent.
The low pH values of the alumina dispersions is necessitated by the fact that the dispersions tend to gel in a pH range of above 4 which, in the case of alumina dispersions, is generally considered to be a neutral range. Indeed, it is well known that many aluminas will not disperse to any acceptable degree using low levels of acids, i.e. high pH values of 4 or above. This is also true of alumina slurries whose dispersion is dependent upon the pH and hence the level of acidity of the slurry.
The necessity of having to use such high acidities in forming stable dispersions of alumina, i.e. dispersions that will not gel, poses significant problems. For one, it is known that aluminas contain trace amounts of impurities which are sensitive to low pH values and which, under high acidic conditions, can affect the alumina properties. Moreover, it will be readily recognized that the high acidic alumina dispersions are corrosive and present handling and transportation problems.
It has also been found that certain alumina slurries, e.g. those derived from Ziegler Chemistry, are essentially unpumpable if the alumina content exceeds about 12% by weight. It will be readily recognized that if the alumina slurry could be concentrated to contain a higher percentage of alumina and still remain a pumpable, free flowing material, shipping costs could be significantly reduced.